Advances in semiconductor manufacturing technology have enabled progress to be seen in the scale finely. In the semiconductor manufacturing of a deep submicron process, the depth of focus shrinks constantly to reach the need for increasing speed and the resolution for lithography raises constantly as well. In order to accomplish the above purposes, global planarization of the wafer surface is highly required, and therefore a CMP process to achieve the goal is also needed.
FIG. 1 shows a conventional CMP apparatus. With reference to FIG. 1, the CMP apparatus constitutes of at least one carrier 110, for holding a semiconductor wafer 120. The carrier 110 holds the wafer 120 against the surface of the polishing pad 130 attached to the rotary polishing platen 131. And the wafer 120 and the polishing pad rotate mutually. During planarization, the wafer 120 oscillates with the polishing pad, and polishing slurry 140 comprised of abrasive fluid, such as silica or alumina abrasive particles suspended in either a basic or an acidic solution, is dispended on the polishing pad and goes into the space between the wafer 120 and the polishing pad 130, through a conduit 141. Then mechanical and chemical polishing effects take place on the wafer 120 between the carrier 110 and the polishing pad 130. The combination of mechanical and chemical polishing effects removes the excessive layers of metal material from the surface of the wafer 120, and accomplishes global planarization.
In the CMP process, the wafer 120 is pressed on the polishing pad 130 because of the downward pressure. Therefore, it is difficult to consistently stop the CMP process at a desired endpoint and to produce a uniform, planar surface on the wafer by measuring the wafer surface. The general statistics shows that two more hours is demanded to measure the wafer surface produced by the conventional CMP process to determine if the wafer surface is planarized well or not. For this reason, the productivity of the CMP process decreases 50%, and the cost of the wafer produced consumes more. The following then says the prior art about the endpoint detection method for the conventional CMP process.
U.S. Pat. No. 5,196,353 entitled “Method for controlling a semiconductor (CMP) process by measuring a surface temperature and developing a thermal image of the wafer” issued on Mar. 23, 1993 to Gurtej S. Sandhu et al. describes the use of an infrared radiation detection in the polishing pad to take the thermal image of the surface of a wafer to adjust the parameters of the process. In application, the surface of a wafer posts to the polishing pad tightly, and therefore it is difficult to take the thermal image of the wafer surface.
U.S. Pat. No. 5,597,442 entitled “Chemical/mechanical planarization (CMP) endpoint method using measurement of polishing pad temperature” issued on Jan. 28, 1997 to Hsi-Chich Chen et al. describes the endpoint for planarization process is determined by monitoring the temperature of the polishing pad with an infrared temperature measuring device. The method determines the endpoint when the temperature decreases by 2° C. In application, it needs to control the temperature of the slurry, and the detected temperature jounces with the slurry. Therefore, it is difficult to determine the endpoint by measuring the polishing pad temperature decreases by 2° C.
U.S. Pat. No. 5,643,050 entitled “Chemical/mechanical polish (CMP) thickness monitor” issued on Jul. 1, 1997 to Lai-Juh Chen et al. describes the method comprises monitoring the temperature of the polishing pad or the polished substrate versus polishing time, integrating the polishing temperature change versus polish time curve with polish time, and applying computer stored integration coefficients to the integrated area to derive the removed thickness. In application, it needs complicated operation processes, and the thickness of the thin film of the wafer surface is not uniform. Therefore, it is difficult to determine the endpoint accurately.
U.S. Pat. No. 5,647,952 entitled “Chemical/mechanical polish (CMP) endpoint method” issued on Jul. 15, 1997 to Lai-Juh Chen et al. describes the method for measuring the temperature of the specific area of the polishing pad, and determining the endpoint by detecting a change in said temperature. In application, it needs to control the temperature of the slurry, and the detected temperature jounces with the slurry. Therefore, it is difficult to determine the endpoint by measuring the polishing pad temperature.
U.S. Pat. No. 5,722,875 entitled “Method and apparatus for polishing” issued on Mar. 3, 1997 to Mitsuaki Iwashita et al. describes the use of an infrared temperature sensor to determine the end point of CMP. In application, the detected temperature jounces with the slurry. Therefore, it is difficult to determine the endpoint. Accurately by measuring a single point temperature of the polishing pad.
U.S. Pat. No. 6,007,408 entitled “Method and apparatus for endpointing mechanical and chemical-mechanical polishing of substrates” issued on Dec. 28, 1999 to Gurtej S. Sandhu et al. describes the method for measuring the temperature of the backside of the substrate, the polishing pad, planarizing liquid, and the CMP byproducts simultaneously. In application, the change temperature of the byproduct is not evident, and the temperature of the byproduct decreases before being detected. Therefore, it is difficult to determine the endpoint accurately.
U.S. Pat. No. 6,077,783 entitled “Method and apparatus for detecting a polishing endpoint based upon heat conducted through a semiconductor wafer” issued on Jan. 20, 2000 to Derryl D. J. Allman et al. describes the method for determining the endpoint by heating a semiconductor wafer so as to cause the surface of the semiconductor wafer to have a specific temperature, and the temperature of said semiconductor wafer changes as the surface of said semiconductor wafer is being removed. In application, the range of the change temperature of said semiconductor wafer would decrease after heat pass the carrier. Therefore, it is difficult to determine the endpoint accurately.
U.S. Pat. No. 6,150,271 entitled “Differential temperature control in chemical mechanical polishing processes” issued on Nov. 21, 2000 to William Graham Easter et al. describes the method for determining the endpoint of the CMP process by installing heating and cooling coils to control the rate of the material removed from the surface of the wafer. In application, the temperature of the carrier easily changes with the influence of environment. Therefore, it is difficult to control the temperature and determine the endpoint accurately.
Thus, there is a strong demand in a method for determining an endpoint of the CMP process accurately and efficiently.